Today it is becoming more and more common to implant different energy consuming devices in a human or mammal body. The implanted devices are typically provided to monitor or control a physiological function or defect in the body of a patient. Historically pacemakers have been the most common implanted medical device but other devices for controlling and monitoring other functions are being developed. For example, today such medical devices include electrical and mechanical stimulators, motors, pumps, etc., which are designed to support or stimulate various body functions. Electrical power can be supplied to such an implanted medical device from a likewise implanted battery or from an external energy transmitter that can supply any needed amount of electrical power intermittently or continuously without requiring repeated surgical operations.
In order to supply energy to an energy consuming implanted device an energy source such as an electrochemical cell or a battery is typically arranged in the implant. Electrochemical cells and batteries have a limited life time. After the electrochemical cell or battery has been emptied or discharged, it has to be re-charged or replaced. In the case of an implanted device it is for several reasons preferred to recharge an electrochemical cell or battery rather than replacing the cell or battery. One reason is the risk associated with removal of the energy source. Other reasons include that some implanted devices consume a relatively large amount of energy and would then have to have their energy sources replaced relatively often.
There is a constant need for improvements in the area of medical devices and the use thereof. Hence, there is a need for improved methods and improved devices for charging an energy source such as an electrochemical cell or a battery associated with an implanted medical device.
Methods and devices for charging a rechargeable energy source are e.g. disclosed in the published U.S. patent application 2005/0075697 and U.S. Pat. Nos. 5,702,431, 5,713,939 and 6,456,883.